Age, Size, and Spatiotemporal Variation in Ovulation Patterns of a Seasonal Breeder, the Norwegian Moose (Alces alces)

• Published in: The American naturalist Vol. 173; no. 1; pp. 89 - 104
• Main Authors: Garel, Mathieu, Solberg, Erling Johan, Sæther, Bernt‐Erik, Grøtan, Vidar, Tufto, Jarle, Heim, Morten
• Format: Journal Article
• Language: English
• Published: Chicago, IL The University of Chicago Press 01-01-2009; University of Chicago Press; University of Chicago, acting through its Press
• Subjects: Age; Aging; Aging - physiology; Alces alces; Animal and plant ecology; Animal physiology; Animal populations; Animal reproduction; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Biological variation; Body regions; Body Size; Deer; Deer - physiology; Female; Female animals; Females; Fundamental and applied biological sciences. Psychology; General aspects; General aspects. Techniques; Geography; Life Sciences; Maturation; Methods and techniques (sampling, tagging, trapping, modelling...); Models, Biological; Models, Statistical; Norway; Other; Ovaries; Ovulation; Parametric models; Physical growth; Reproduction; Seasons; Ungulates; Yearlings; Norway; life-history theory; body mass; ungulates; age; ecological modeling; reproduction; Life history; Theory; Body weight; Alces alces; Ecology; Spatial variation; Modeling; Time variation; Vertebrata; Reproduction; Mammalia; Seasonal variation; Artiodactyla; Ungulata; Age
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/593359

In seasonal environments, timing of reproduction is an important fitness component. However, in ungulates, our understanding of this biological process is limited. Here we analyze how age and body mass affect spatiotemporal variation in timing of ovulation of 6,178 Norwegian moose. We introduced a parametric statistical model to obtain inferences about the seasonal timing of ovulation peak, the degree of synchrony among individuals, and the proportion of individuals that ovulate. These components showed much more spatiotemporal variation than previously reported. Young (primiparous) and old (≥11.5 years of age) females ovulated later than prime‐aged (2.5–10.5 years of age) females. In all age classes, ovulation was delayed with decreasing body mass. Ovulation rates were lower and more variable among primiparous females than among older females. Young females required higher body mass than older females did to ovulate. The body‐mass‐to‐ovulation relationship varied with age, showed large regional variation, and differed among years within region. These results suggest that (1) environmental and population characteristics contribute to shape seasonal variation in the breeding pattern and (2) large regional variation exists in the size‐dependent age at maturity in moose. Hence, the life‐history trade‐off between reproduction and body growth should differ regionally in moose.